The default /etc/mplayer.conf in mplayer-1.0_pre6 includes the following two options:
# Prefill 20% of the cache before starting playback.
cache_min = 20.0
# Prefill 5% of the cache before restarting playback after the cache emptied.
cache_prefill = 5.0
Both of these options are no longer supported:
Warning unknown option cache_min at line 144
Warning unknown option cache_prefill at line 147
I don't seem to see any indication that this bug is on our side. Feel free to re-open the bug with an explination of what in the ebuild is causing the issue. The cache patch (the only file that would) is not in pre6.